wrote in message
...

Oil rigs seem to be capable of drilling holes inches in diameter
and thousands of feet deep. They can keep these holes amazingly
straight or deliberately curve them.

How do they do this and what does the drill head look like?

Jim

Oilwells are drilled with predetermined goals in mind. The target strata is
not always right under the oil rig. Hence, they use "directional drilling"
to make the bit go in the direction they want it to. That way, they can
puncture several levels of strata with one well to recover as much oil as
they can.

Directional drilling is achieved in many ways. It is far to complicated to
explain here in a few paragraphs. Google it and read away. Basically, it
is just a way to change the direction of a bit to hit a known reserve.
Modern advances allow drillers to make sharper turns. A drillstem is made
of steel, but anything thousands of feet long has flex in it.

Drill bits come in hundreds of sizes and configurations. Some have no
rolling bits on them. Others have rolling cutting wheels on them like the
ones you see on mining equipment. They come in all sizes.

Hughes Tools was innovative in the oil industry. NO ONE could purchase a
Hughes Tool Bit. You could only rent them. That way, there was absolutely
no question as to ownership. When one went dull or was damaged or lost, you
got another.

Google for oilwell drill bits, and read on.

Steve